4. Discussion
Since the emergence of SARS-CoV-2 at the end of 2019, a broad range of
strategies, notably NPIs, have been globally implemented to combat the
virus. These measures, including city lockdowns, social distancing, use
of personal protective equipment, and enhanced hygiene practices, have
substantially reduced coronavirus transmission. The application of NPIs
has notably interrupted the usual seasonal patterns of common
respiratory viruses. A marked decrease in influenza and Respiratory
Syncytial Virus (RSV) cases was observed following NPI
implementation[21]. In contrast, Rhinovirus (RV)
infections exhibited an increasing trend. This is supported by studies
from New Zealand, which reported a high incidence of RV infection during
the pandemic[22]. Furthermore, a study in Suzhou,
China, involving 10,396 viral respiratory infection cases, identified RV
as the most frequently detected virus, accounting for 23.3% of
infections[23]. Between January 2021 and December
2023, our study included 19,680 pediatric inpatients with ARTIs. Of
these, 21.55% tested positive for RV, peaking in April 2021 and
November 2022. A year-on-year decrease in RV infections was noted,
declining from 24.36% in 2021 to 19.67% in 2023. Seasonal fluctuations
in RV infections aligned with existing literature, demonstrating a
higher prevalence in autumn, winter, and spring. The study observed that
the 0-1 year age group had the highest proportion of RV infections.
Significant variations in infection rates across different age groups
were noted, predominantly in children under three years. Phylogenetic
analysis revealed 23 distinct RV subtypes, with RV-A and RV-C being the
most common. A significant shift in the dominance between RV-A and RV-C
in 2022 indicated a dynamic pattern in RV circulation and genetic
diversity. The study also investigated the correlation between RV
subtypes and clinical characteristics, finding a predominance of RV-C in
asthmatic patients and a higher incidence of severe RV-associated Lower
Respiratory Tract Infections (LRTIs) in males. This study explores the
epidemiological shifts in RV infections among children on Hainan Island,
emphasizing the effects of the termination of the zero-COVID policy in a
region with distinct climatic and geographical characteristics.
In March and August 2022, Hainan, China, experienced two COVID-19
pandemic. In response, strict NPIs were enforced throughout the year,
until the lifting of zero-COVID policies. Despite the implementation of
preventive measures, a significant reduction in RV infections was not
evident, suggesting that the efficacy of face masks in curbing RV
transmission might have diminished during this period. RV is a
non-enveloped virus known for its relative resistance to disinfectants
containing ethanol and its ability to survive on environmental surfaces
for extended periods transmission[4, 5]. While
medical masks are effective in blocking large droplets and aerosols,
they may not provide adequate protection against smaller particles like
RV. This may also be one of the main reasons why RV infection rates
remained high during the COVID-19 epidemic. Notably, with the advent of
the Omicron variant and a substantial increase in vaccination rates,
governments worldwide have begun to roll back these stringent measures,
aiming to normalize social activities. This policy shift has led to an
increase in reports of respiratory virus resurgence[20]. According to monitoring by the World Health
Organization, after a significant reduction in the transmission of
respiratory viruses globally during the COVID-19 pandemic, there has
been a marked increase in the activity level of respiratory viruses
across the world [22]. On 7 December 2022, China’s
modification of the dynamic zero-COVID-19 policy precipitated a
widespread outbreak of COVID-19 in the following months. This
alteration, together with the relaxation of non-pharmaceutical
interventions (NPIs) and social distancing measures, is presumed to have
impacted the epidemiology of other respiratory tract infections.
Particularly, an increase in influenza A virus infections among children
was noted in Shanghai after the policy change[17].
The concept of viral interference, involving interactions between
influenza virus, rhinovirus, and other respiratory viruses, is a
plausible factor in the decreased prevalence of RV infections observed
in pediatric inpatients with ARTIs in 2023. This suggests a complex
interplay of viral interactions within the evolving public health
context.
The study demonstrated that, during the COVID-19 epidemic period, RV
infection rates on Hainan Island were highest in children under three
years old. Furthermore, the prevalence of RV infections diminished
progressively with increasing age. This trend is likely due to the
development of cumulative immunity from repeated exposure to diverse RV
serotypes. Notably, a substantial number of RV cases were recorded in
children under three, with toddlers being particularly prone to
infection. Given the elevated infection rates in this demographic, our
findings underscore the importance of targeted prevention and healthcare
strategies. Effective measures include enhancing hygiene practices,
advancing vaccination efforts, and educating parents and caregivers
about RV risks and preventive methods, aiming to alleviate the disease’s
impact on young children. Our investigation further identified a notable
gender-based disparity in RV infection rates, exhibiting a predominance
in male children. This observation contrasts with certain earlier
reports. Specifically, Haixia Jiang et al. analyzed 5,832 nasopharyngeal
swabs collected from patients with acute respiratory infections spanning
2012 to 2020, finding a RV infection rate of 2.74% (160/5832), with no
significant gender disparity in the patient cohort[5]. Similarly, a study by Wanwei Li, Lili et al.,
which examined nasopharyngeal swabs from 655 patients suffering from
ARTIs, also reported no significant gender difference among those
infected with rhinovirus [6]. This divergence in
findings underscores the complexity of RV transmission dynamics and
suggests the influence of additional, possibly region-specific, factors
affecting susceptibility and infection rates among different
demographics.
Seasonal variation, characterized by changes in humidity, temperature,
and climate, serves as an external factor that can significantly
influence the severity of viral illnesses. Studies on rhinovirus (RV)
patterns in different climatic conditions reveal contrasting findings:
while RV detection peaks during the rainy seasons in Malaysia and Latin
America, increased RV activity is observed in the dry seasons of Brazil
and Cambodia. The RV infections predominantly occurred in autumn,
winter, and spring on Hainan Island. Given its tropical setting, the
island experiences its rainy season from May to October, suggesting a
complex relationship between seasonal patterns and RV infection rates,
which may not solely depend on precipitation levels.
Phylogenetic analysis identified three RV species among the positive
samples: RV-A (46.88%), RV-B (6.25%), and RV-C (46.88%) in Hainan
Island. It was found that RV-A and RV-C are the primary strains
transmitting rhinovirus on Hainan Island, with multiple types
circulating simultaneously. Our study highlighted a significant temporal
transition in RV strain dominance, with RV-C surpassing RV-A to become
the predominant strain starting in October 2022. This shift coincided
with a peak in RV infection rates in November 2022, the highest observed
in the past three years, potentially linked to specific epidemic strain
subtypes and variations in annual weather patterns. Additionally,
international research highlights significant genotype variations in
circulating rhinoviruses, related to both time and geographical
factors[24, 25]. The consistent identification and
seasonal variation in the dominance of RV-A and RV-C strains across
these studies reflect our findings, emphasizing the prevailing influence
of these strains.
Previous studies have suggested that RV-C might play a role in severe
clinical disease [26]. RV-C was present in the
majority of children with acute asthma and was associated with more
severe asthma[27, 28]. Wheezing episodes were also
more common among individuals with RV-C and RV-A infection than among
those with RV-B infection[26]. Another study
suggested that RV-C was associated with more severe disease in children
<3 years of age[29]. However, some
reports found no differences in the clinical characteristics among
hospitalized enrolled patients positive for RV-A, RV-B, or RV-C,
including wheezing[30]. In our study, we observed
that patients infected with RV-A tended to be younger compared to
patients infected with RV-C. Additionally, we also noted that children
infected with RV-C were more likely to exhibit clinical symptoms of
wheezing. These findings suggest that there are differences in age
distribution and clinical presentation between RV-A and RV-C. In our
analysis, patients were divided into groups based on the severity of
Lower Respiratory Tract Infections (LRTIs), showing no significant
age-related differences between these categories. Notably, a greater
occurrence of severe RV-associated LRTIs was identified in males, with
85.71% of severe cases found in boys, introducing potential
gender-specific variations in disease severity. Additionally, the study
revealed that children with asthma histories were more susceptible to
severe LRTIs and extended hospitalizations, supporting the theory that
pre-existing respiratory conditions can amplify RV infection
impacts[31, 32]. This emphasizes the importance of
vigilant monitoring and possibly specialized treatment approaches for
asthmatic children with RV infections.
This study faces several limitations that merit attention. Firstly, all
samples were sourced exclusively from Hainan Maternal and Child Health
Hospital, the largest tertiary pediatric hospital in Hainan, which
predominantly treats severe cases of childhood illnesses. While this
facility’s prominence lends weight to our findings, the single-center
nature of the analysis introduces potential biases, as it may not fully
represent the broader pediatric population of Hainan Island. Secondly,
RV subtypes were identified in only 32 RV-positive samples collected at
different times. This sample size is too limited to comprehensively
reflect the variety of RV subtypes circulating across Hainan Island.
Future studies that include a wider range of collection sites
encompassing more hospitals and regions on Hainan Island, along with an
expanded analysis of RV subtypes, are crucial for a more complete
understanding of the epidemiology of RV infections in this area.